1. Field of the Invention
This disclosure relates to ceramic-containing armor composites for articles, supports and vehicles, including aircraft vehicles, such as helicopters, and the fabrication methods. More particularly, the disclosure relates to polymer infiltrated felts and polymer-derived ceramics used for combat vehicle armor. Still more particularly, the disclosure relates to ceramic armor composites having a hard phase combined with an energy absorbent structure and the fabrication methods. One embodiment of this disclosure contains a hard outer surface and an energy absorbent inner core.
2. Description of Related Art
In the combat environment there is a continuing and ongoing need to provide improved ballistic protection to various vehicles, e.g., aircraft and helicopters. During combat, helicopters are extremely vulnerable to sniper attacks. Current armor technology is capable of providing Type IIIA protection, and typically contains fiber-reinforced polymer composite, for example, glass or Kevlar® reinforced thermoplastic.
In heavily armored helicopters, components are designed to withstand 12.7 mm rounds, with vital engine and rotor components designed to be capable of withstanding 23 mm or larger fire. Enhanced armor, such as that offering Type IV protection, is often a composite structure that incorporates a thick, solid metal plate or a dense ceramic phase to produce the desired degree of hardness. Such armor is often heavy (which is undesirable for example in flight vehicles), difficult to manufacture in a cost effective manner, and limited to simple geometries such as flat structures with minimal curvature. During use, the impact force of projectiles is often inadequately distributed in such armor because the hard phases in the composite are poorly integrated with a more compliant structure or flexible backing component. Such backing components are generally fabricated with layers of organic polymer fiber-based cloth or fabrics to provide strength and toughness. In practice, armor is designed so that the hard face breaks upon impact with the incoming round, thereby damaging the round, and the compliant backing structure provides additional resistance to travel by the broken hard face or damaged round.
Ceramics presently in use for armor are of a composite nature having the ceramic hard surface and the more deformable polymer based backing. The ceramic surface is generally silicon carbide (SiC), boron carbide (B4C), alumina is (Al2O3), zirconia (ZrO2), silicon nitride (Si3N4), spinels, aluminum nitride (AlN), tungsten carbide (WC), titanium diboride (TiB2) and combinations thereof. The materials used for the backing are often fibrous and include materials such as glass, polyimide (Kevlar®) and polyethylene (Spectra®, Dyneema®).
The methods for manufacturing such composites have numerous limitations. Currently, their fabrication methods limit the armor configurations to flat plates or simple planar geometries or modestly curved shapes. Such armor is very heavy and can negatively impact maneuverability of the vehicle. The associated fabrication methods typically require high temperatures, e.g., above 1500° C., and often above 2000° C., and pressures above 2000 psi. Such fabrication requirements are costly, energy consuming, slow and not generally suitable for mass production. For example, complex and expensive tooling or die sets are generally required to form such armor structures. As a result, lightweight, highly curved armor configurations with Type IV protection derived from ceramic composites are not presently available.
Accordingly, there is a need for lightweight, highly curved ceramic composites that offer ballistic or blast protection that can be easily fabricated using a wide variety of composite architectures suitable for different combat applications.